Approximately one out of every fifteen children entering elementary school in the U.S. has a significant developmental language impairment of unknown origin. Detailed studies of speech acoustics have significantly improved understanding and treatment of language impairments. These studies also provide the foundation needed to investigate the neural representation of speech. While peripheral representations have been extensively studied, relatively little is known about the cortical mechanisms that contribute to speech processing. The objective of this proposal is to define the distributed response of mammalian auditory cortex neurons to human speech sounds and to determine what experience-dependent changes in the neural representation of speech are possible. The first aim of the project will be to precisely document the distributed response of auditory cortex neurons to speech sounds. Our preliminary results (from awake and anesthetized recordings in two distinct auditory fields) indicate that frequency bandwidth and forward masking time course appear to account for speech responses of most auditory cortex neurons. The second aim will be to document the distributed cortical response to exaggerated speech sounds that have been used to treat language-learning impairments in thousands of children. Our initial findings indicate that the cortical activity patterns generated by modified speech are more distinct than the patterns generated by natural speech sounds. The third aim will be to establish how cortical neurons are modified by exposure to natural and modified speech sounds. The results of the proposed studies will add to our understanding of neural mechanisms that could contribute to speech processing and learning in human auditory cortex. Insights derived from these studies will influence the use and development of behavioral and sensory rehabilitation of language impairments.